Radiation force on a nonlinear microsphere by a tightly focused Gaussian beam.
Radiation force on a nonlinear microsphere by a tightly focused Gaussian beam.
复制标题
DOI：
10.1364/ao.41.007694
复制
发表时间：
2002-12
期刊：
影响因子：
1.9
通讯作者：
R. Pobre;C. Saloma
中科院分区：
文献类型：
--
作者：
R. Pobre;C. Saloma
我们确定了当衍射和干涉效应很大(球体半径a和lt；或=照明波长波长)时，强聚焦高斯光束对非共振非线性(克尔效应)刚性微球施加的辐射力的特性。平均力由能量动量张量的表面积分计算，能量动量张量由入射、散射和内部电磁场向量组成，表示为多极球面波展开。克尔微球的折射率与内场强度成正比，内场强度由Rytov近似迭代计算(解的残差为10(-30))。根据近似的索引值计算场向量的展开系数。与相同光照条件下的介质(线性)微球相比，我们发现克尔微球上的力大小更大，并且随着聚焦物镜的数值孔径的增大而迅速增大。与线性球体不同的是，它也随着光束功率呈非线性增加。克尔非线性也可能导致力方向的反转。该方法也适用于其他类型的弱光学非线性。
We determine the characteristics of the radiation force that is exerted on a nonresonant nonlinear (Kerr-effect) rigid microsphere by a strongly focused Gaussian beam when diffraction and interference effects are significant (sphere radius a < or = illumination wavelength lambda). The average force is calculated from the surface integral of the energy-momentum tensor consisting of incident, scattered, and internal electromagnetic field vectors, which are expressed as multipole spherical-wave expansions. The refractive index of a Kerr microsphere is proportional to the internal field intensity, which is computed iteratively by the Rytov approximation (residual error of solution, 10(-30). The expansion coefficients for the field vectors are calculated from the approximated index value. Compared with that obtained in a dielectric (linear) microsphere in the same illumination conditions, we find that the force magnitude on the Kerr microsphere is larger and increases more rapidly with both a and the numerical aperture of the focusing objective. It also increases nonlinearly with the beam power unlike that of a linear sphere. The Kerr nonlinearity also leads to possible reversals of the force direction. The proposed technique is applicable to other types of weak optical nonlinearity.